Exterior autobody part of reinforced plastic, and arrangement and method for its forming

ABSTRACT

An exterior autobody part of reinforced plastic intended to be mounted on a motor vehicle. The expression “exterior autobody part” refers to the autobody part being entirely or partly visible when the motor vehicle is viewed from the outside. Furthermore, the invention relates to a method and an arrangement for forming such an exterior autobody part. The exterior autobody part according to the invention comprises a number of functional layers, including load-bearing layer(s) and surface layer(s), intended to provide the properties which are required for the application, and is characterized in that load-bearing layers comprise(s) fiber-reinforced thermoplastic which forms internal cavities and/or that one or several recesses has/have been created in surface layers and load-bearing layers and that surface layers and load-bearing layers together with cavities and/or recesses thereby provide a load-bearing material structure. Examples of properties essential for the application are low weight, high stiffness, and durability, recyclability and visual properties. The invention can be applied within the field of externally visible motor vehicle parts, for example boot lids and wind deflectors.

TECHNICAL FIELD

The present invention relates to an exterior autobody part of reinforcedplastic, intended to be mounted on a motor vehicle. The expression“exterior autobody part” refers to the part being entirely or partlyvisible when the motor vehicle is viewed from the outside.

The invention further relates to a method and an arrangement for formingsuch an exterior autobody part.

The invention pertains to the fields of reinforced thermoplasticcomposites or laminates and vacuum forming of thermoplastic components.

The exterior autobody part according to the invention comprises a numberof functional layers, intended to provide the properties which arerequired for the application. Examples of such properties are lowweight, high stiffness and durability, recyclability and visualproperties.

The invention can be applied within the field of motor vehiclecomponents which are visible from the exterior of the vehicle, forexample boot lids or wind deflectors.

BACKGROUND OF THE INVENTION

Within the field of sports equipment, a vacuum forming process ispreviously known for manufacturing thermoplastic articles, for examplewind-surfing boards. The process utilizes two sheet-shaped materialbatches which are clamped in a clamping device and is therefore usuallycalled “twin-sheet”. The two braced material batches are heated andcomprise thermoplastic material and, during the forming, function aselastically stretchable membranes which, by means of external vacuumand/or internal pressure acting on the membranes, are formed accordingto the inner contours of an enclosing, cooled forming device. By meansof this previously known forming process, different hollow plasticarticles which comprise thermoplastic material can be obtained.

Within the field of conventional exterior autobody parts for motorvehicles, for example boot lids, autobody parts of body panel sheets or,for example, of glass-fibre reinforced thermosetting plastic arepreviously known.

Conventional exterior autobody parts of sheet metal are manufacturedthrough different metal working operations comprising rolling, pressing,bending and welding. Such sheet metal parts usually also compriseseparate reinforcements in the form of stiffening profiles and similarcomponents, which are manufactured and mounted in separate steps.

After the forming and/or mounting of a conventional exterior autobodypart of sheet metal, different surface finishing and polishing stepsfollow in order to provide the finished autobody part with aestheticallypleasant and corrosion-protected surfaces on both the inside and theoutside of the autobody part.

Where previously known exterior autobody parts of glass-fibre reinforcedthermosetting plastic or other thermosetting plastic composites areconcerned, such parts are manufactured in a process with several formingor laminating steps with the use of reinforcement material, for exampleglass-fibre mats, and thermosetting matrix material, for example vinylester resin. After the forming of the reinforcement material and theimpregnation thereof with thermosetting matrix material, a relativelytime-consuming curing follows which, for instance, may take place withina moulding or pressing tool. Thereafter, the exterior autobody part ofreinforced thermosetting plastic generally has to be surface-finishedand polished further in order to obtain surfaces with a surface finishof sufficient quality for the application.

The above-mentioned, previously known, exterior autobody parts can beperceived as having certain disadvantages. Where autobody parts ofconventional sheet metal are concerned, it may be difficult to achieve asufficiently low autobody part weight in order to fulfil the everincreasing demands upon low fuel consumption and low emissions to theenvironment which are placed upon the motor vehicles of today.Furthermore, separate surface finishing and surface polishing lines arerequired in order to provide material surfaces with the desiredproperties to the finished sheet metal parts.

Where parts of glass-fibre reinforced thermosetting plastic areconcerned, the relatively time-consuming thermosetting process, and thedemands for separate surface finishing and polishing steps, may beperceived as difficult. Furthermore, it is difficult to recover andrecycle composite materials of thermosetting plastic.

SUMMARY OF THE INVENTION

Accordingly, the first object of the present invention is to provide anexterior autobody part of reinforced plastic, intended to be mounted ona motor vehicle, which part is recyclable in a simple way and which,without any separate reinforcements and in spite of low weight, providessufficient stiffness and durability, and which does not require anytime-consuming curing when manufactured.

This object is achieved by means of the exterior autobody part accordingto the invention comprising load-bearing layer(s) and surface layer(s)and that the load-bearing layer(s) comprise(s) fibre-reinforcedthermoplastic which forms internal cavities and/or that one or severalrecesses has/have been created in the surface layers and theload-bearing layers, and that the surface layer(s) and the load-bearinglayers(s) together with cavities and/or recesses provide a load-bearingmaterial structure.

A second object of the present invention is to provide an autobody partof reinforced plastic, intended to be mounted on a motor vehicle, havinga surface finish with a sufficient quality in order not to require anyspecial surface finishing in the form of grinding or the like beforepainting, or which provides a surface finish of a sufficient quality inorder to be left unpainted.

This object is achieved by means of the exterior autobody part accordingto the invention providing at least one decorative layer, betweensurface layer and load-bearing layer, and that the surface layer(s) andthe decorative layer(s) together provide at least one external surfacewhich provides the main portion of the visual effect and the surfaceproperties which the exterior autobody part should exhibit when mountedon a motor vehicle, and that surface layers, decorative layers andload-bearing layers all comprise a thermoplastic and have been formedtogether under heating.

A third object of the present invention is to provide an arrangement forforming an exterior autobody part according to the invention.

This object is achieved by means of the arrangement according to theinvention comprising a forming tool with tool halves, arranged to beopened and closed in order to create an internal form cavity, and thatthe arrangement comprises material holders intended for clamping atleast one material batch with thermoplastic material, heating means forheating the material batch, pressurizing connection and vacuumconnection intended to generate, by means of internal pressurization andexternal vacuum application, a forming force on the material batchfunctioning as a stretchable membrane after heating, and cooling meansintended to cool down the heated material batch after forming inside theform cavity, and that the material batch comprises at least oneload-bearing layer with reinforcement fibres.

Furthermore, a fourth object of the present invention is to provide asimple and effective method for forming an exterior autobody partaccording to the invention.

This object is achieved by means of the method according to theinvention comprising the use of a forming tool with first and secondtool halves arranged to be opened and closed in order to create aninternal form cavity, and that thereby at least one material batch withthermoplastic material is clamped between the tool halves in an openposition by means of material holders, after which the material batch bymeans of heating means is heated to or above the softening temperatureof the thermoplastic material, that the tool halves are thereafterclosed around the material batch while a vacuum is applied between thematerial batch and the first tool half, wherein the material batchfunctions as a stretchable membrane and is formed according to theinternal surface of the first tool half, after which cooling means inthe tool halves gradually cools down the material batch to a temperaturebelow the softening temperature, that the tool halves are brought intoan opened position and that thereafter a blank is removed from theforming tool in order to provide, after trimming and making of holes, anexterior body part of reinforced plastic with a load-bearing structure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to theattached drawings, in which

FIG. 1 shows a schematic cross-section of a portion of an exteriorautobody part according to the invention,

FIG. 2 illustrates schematically in the sub-FIGS. 2A to 2D a methodaccording to the invention practised by means of an arrangementaccording to the invention, and

FIG. 3 shows an external perspective view of the driver's cab of atruck, wherein one of the body panels visible in the drawing isconstituted of an exterior autobody part according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the attached FIG. 1, a schematic cross-section of an exteriorautobody part of reinforced plastic, according to a first preferredembodiment of the invention, is shown. The shown cross-section is aportion of a boot lid for a motor vehicle, wherein the upward surface inthe drawing corresponds to the outside of the boot lid when this ismounted on a motor vehicle, whereas the downward surface in the drawingcorresponds to the inside of the boot lid.

Thus the exterior body part shown in FIG. 1 from the outside inwards,i.e. from top to bottom in FIG. 1, comprises a first surface layer 1, afirst decorative layer 2, a first structural layer 3 and a firstload-bearing layer 4. Thereafter one or several cavities 5, 5′ follow,which have been created during the forming in suitable positions insidethe structure of the exterior autobody part according to the invention.

Thereafter, counted from top to bottom in FIG. 1, i.e. inwards on thevehicle, there follows a second load-bearing layer 4′, a secondstructural layer 3′, a second decorative layer 2′ and finally, i.e.facing towards the inside of the boot lid, a second surface layer 1′.

In a portion of the exterior body part according to the invention shownin FIG. 1, a recess 6 or groove has been impressed, using a formingtool.

When comparing an exterior autobody part according to the invention witha conventional exterior autobody part of painted sheet metal, theload-bearing layers 4, 4′ and the cavities 5, 5′ according to theinvention together can be said to correspond to the structure which isformed by the sheet metal of a conventional autobody part. Thestructural layers 3, 3′ can be said to correspond to a layer of thesheet metal with layers of primer/rust finish, the decorative layers 2,2′ can be said to correspond to the surface paint, whereas the surfacelayers 1, 1′ of the exterior autobody part according to the inventioncan be said to correspond to external clear varnish of the conventionalbody part.

The recess 6 contributes to high stiffness of the exterior autobody partaccording to the invention and therefore can be said to correspond to astiffening profile or beam in a conventional sheet metal part.

Because of the structure which is created by the two load-bearing layers4, 4 with cavities 5, 5′ enclosed therebetween, the exterior body partaccording to the invention provides a so-called sandwich structure withlow weight but still with a sufficiently high stiffness and load-bearingability for the application. Further more, the recess 6 created in theforming contributes to the stiffness of the sandwich structure.Accordingly, the exterior autobody part according to the inventionrequires no additional reinforcements in the form of attached profilesor beam structures.

Furthermore, the structural layers 3, 3′, the decorative layers 2, 2′and the surface layers 1, 1′ together provide external surfaces to theexterior autobody part according to the invention with the surfaceproperties required for the application. Amongst such surfaceproperties, visual decorative effect (e.g. colour and gloss), impact andscratch resistance, and also dirt and water repellent properties can bementioned. Accordingly, the exterior autobody part according to theinvention requires no special surface finishing in the form of grindingor the like before possible painting or varnishing or can preferably beleft unpainted.

In the following, with reference to the attached FIG. 2, preferredembodiments of a method and an arrangement according to the inventionwill be described.

The method according to the described embodiment utilizes twosheet-shaped material batches 10, 11 which can be said to constitutepart of an arrangement according to the invention. A first, essentialtask of the material batches is of course to provide raw material forthe forming of an exterior autobody part according to the invention,wherein the two sheet-shaped material batches together comprise thedifferent functional layers which have been described above.

In the described embodiment, the two material batches 10, 11 areintended to be clamped mirror-inversely against each other between thetool halves 12, 13 of a forming tool, so that the layers which areintended to constitute the above-mentioned load-bearing layers arefacing each other.

In the described embodiment, the two material batches 10, 11 consist ofa multilayered material which has been manufactured by means ofextrusion in a so-called multi-layer extruder. In principle, amulti-layer extruder consists of several individual extruders, thenozzles of which are arranged to be able to, preferably simultaneously,extrude several different melted thermoplastic layers on top of eachother in order to obtain a multilayered material with different materialcomposition in different layers.

In the first embodiment, the multilayered material which is used for thetwo material batches comprises a 0.2 mm thick extruded firstpolymetachrylate layer (PMMA). After the forming, this layer is intendedto constitute one of the above-mentioned surface layers of the exteriorautobody part according to the invention.

Inside the first PMMA-layer, a second 0.2 mm thick extruded PMMA-layerwith an addition of colouring pigment follows. The colouring has beenachieved by means of using PMMA-granules with an pigment addition whenextruding this layer. After forming, this layer in intended toconstitute one of the above-mentioned decorative layers of the exteriorautobody part according to the described first embodiment of theinvention.

Inside the two PMMA-layers there follows an extruded layer ofacrylo-butadiene styrene plastic (ABS) with 1.6 mm thickness. In thedescribed embodiment, also the ABS-layer contains an addition ofcolouring pigment. After forming, this layer is intended to constituteone of the above-mentioned structural layers of the exterior autobodypart according to the invention.

Finally, the multilayered material outside the ABS-layer comprises alayer of extruded, glass fibre-reinforced ABS-plastic with 3.0 mmthickness. After forming, this layer is intended to constitute one ofthe above-mentioned load-bearing layers of the exterior autobody partaccording to the invention.

When manufacturing an exterior autobody part according to the describedembodiment, as shown in FIG. 2A, two material batches 10, 11 of theabove-described type are clamped in parallel to each other by means ofthe material holders 14, 15 of a forming tool with its tool halves 12,13 in an opened position. Thereby, the forming tool is of a type whichis previously known for forming in accordance with the above-mentionedtwin-sheet process.

In the described embodiment, in connection with the forming tool,heating means in the form of two sets of IR-lamps or IR-ramps 16, 17 inpairs are provided, which are intended for heating of theabove-mentioned material sets 10, 11.

By means of a therefore intended actuating means (not shown), the twoIR-ramps 16′, 17′ are displaced into the open forming tool so that theyarrive at a position between each material batch 10′, 11′ and each toolhalf 12′, 13′. This situation is shown in FIG. 2B.

Thereafter, in a heating stage, the two material batches 10′, 11′ areheated to approximately 250° C. by means of activating the IR-lamps ofthe IR-ramps 16′, 17′.

In the described embodiment, the forming tool is arranged in such a waythat it is possible to apply an over-pressure between the materialbatches 10, 11, as well as between the lower tool half 13 and the lowermaterial batch 11. Such a pressurization is attained by means of firstpressurizing connection 18, arranged so that it exits between the twomaterial batches 10, 11, and by means of second pressurizing connection19, which exits between the lower material batch 11 and the second toolhalf 13.

Furthermore, by means of the first 20 and second 21 vacuum connections,vacuum can be applied between the upper tool half 12 and the uppermaterial batch 10, and between the lower tool half 13 and the lowermaterial batch 11.

In the described embodiment, pressurization via the pressurizingconnections 18′, 19′ takes place in connection with the heating phase,shown in FIG. 2B, with the purpose of avoiding deflection caused by theelongation which arises in the material batches 10′, 11′ when they areapproaching the softening temperatures of the constituentthermoplastics.

When the material batches 10′, 11′ have been heated to approximately 250° C., the two IR-ramps 16″, 17″ are withdrawn from the forming tool,after which the tool halves 12″, 13″ are closed around the thereinenclosed, heated material batches 10″, 11″. Such a situation is shown inFIG. 2C.

Thereafter, vacuum is applied between the upper tool half 12″ and theupper material batch 10″ via the first vacuum connection 20″, andbetween the lower material batch 11″ and the lower tool half 13″ via thesecond vacuum connection 21″. Simultaneously with the vacuumapplication, the space between the two material batches 10″, 11″ ispressurized via the pressurizing connection 18″.

The simultaneous internal pressurization and external vacuum applicationresult in the heated material batches 10″, 11″, inside the closedforming tool shown in FIG. 2C, being formed according to the form cavitycreated by the closed tool halves 10″, 11′.

In the two tool halves 12″, 13″, cooling means 22″ and 23″ are arranged,which in the described embodiment comprise cold water coils.

When the forming of the heated material batches shown in FIG. 2C hastaken place, the formed material batches will gradually be cooled downby means of the cooling means 22″, 23″. This implies that thethermoplastic material included in the material batches graduallysolidifies when the temperature falls below the softening temperature.

When the material batches 10″, 11″ have been cooled down sufficiently,the tool halves are opened and a blank 24 for an exterior autobody partaccording to the invention is removed from the forming tool. The twomaterial batches have now been consolidated and have adopted a shape,the outer dimensions of which essentially correspond to the dimensionsof the form cavity which is created inside the forming tool when the twotool halves are in a closed position. Because of the pressurization andvacuum application, cavities 25, 25′, and portions 26 in which the twomaterial batches are attached to each other by thermal bonds, have beencreated.

During the forming process, as a rule, the thickness of the layersincluded in the two material batches is reduced by approximately half ofthe original thickness.

After necessary after-treatment, such as for example trimming and makingof holes for attachments and the like, an exterior autobody part 27according the invention, intended to be mounted on a motor vehicle, isobtained.

In the described embodiment, the exterior autobody part according to theinvention is intended to be used for a boot lid of a motor vehicle andis ready for mounting directly after the manufacture.

However, even if such embodiments are less advantageous, it is alsoconceivable with embodiments in which the exterior autobody partaccording to the invention is painted or varnished in a separate stage.

In preferred embodiments of the invention, no separate painting isneeded, something which provides environmental advantages.

Furthermore, the exterior autobody part according to the invention isbased on thermoplastic, which offers great possibilities for materialrecovery, since thermoplastic can be melted and reused when extrudingnew plastic components.

In particularly preferred embodiments of the invention, the constituentthermoplastics are blendable with each other, for example in extrusion,something which further facilitates material recovery.

In principle, an imaginary recycling of an exterior autobody partaccording to the invention, for example a boot lid for a motor vehicle,could be achieved in the following steps:

1) coarse shredding of the part together with metal components such aslocks and the like,

2) metal separation,

3) fine milling,

4) preparation of granules of recycled thermoplastic, and

5) admixing a certain proportion of the granules when extruding a newmultilayered material for use in material batches when manufacturing newexterior autobody parts.

A recycling process as described above can, with great advantage, beused for the recovery of waste which is generated in the formingprocess, but could also be used for recovering exterior autobody partsaccording to the invention from scrapped motor vehicles.

The present invention is in no way limited to what has been disclosed inconnection with the preferred embodiments or to what is shown in theattached drawings, but the scope of the invention is defined by theattached claims.

Accordingly, it is also conceivable with less preferred embodiments ofthe invention in which a single material batch is utilized and that thematerial batch by means of vacuum application and/or pressurizationthereby acts like a stretchable membrane which is formed against aninternal surface of a forming tool. In such a case, the exteriorautobody part according to the invention obtains no internal cavity andtherefore has to be provided with through profiles, folds or edgesduring the forming, in order to be able to provide sufficient stiffnessand load-bearing ability.

The composition of the layers which are included in the exteriorautobody part according to the invention can be varied to a high degree.Thereby, a large number of thermoplastics are conceivable as long as thethermoplastic material is able to provide the properties required forthe application, for instance, when heat resistance, impact resistance,surface hardness, stiffness etc. are concerned. In addition to theabove-mentioned ABS- and PMMA-thermoplastics, polypropylene (PP) can bementioned.

When the reinforcement material included in the load-bearing layers isconcerned, this can comprise both cut and continuous fibres, which canbe provided, for example, in the form of individual fibres, in the formof a nonwoven material with individual fibres, or in the form of awoven, knitted or braided textile fabric. In connection with theextrusion, however, the reinforcement material must be possible tointegrate into the multilayered material which is to be used for thematerial batches used in the forming process. Suitable reinforcementfibres are advantageously selected amongst fibres with high stiffnessand tenacity, such as glass fibres, carbon fibres, kevlar fibres, nomexfibres, polyester fibres or aramide fibres.

There is also a large number of different additives which might beconceivable as admixtures when manufacturing raw material for exteriorautobody parts according to the invention. Examples of such additivesare colouring pigments, uv-stabilizers and flame-proofing agents.

Furthermore, it should be noted that the temperature, pressure andvacuum levels, which are used for pressurization and vacuum applicationin connection with the forming, have to be set separately for eachindividual case, depending on raw material, layer thicknesses etc. Suchas adaptation, however, can comparatively easily be performed by askilled person within the field.

In the foregoing, it has been mentioned that the exterior autobody partaccording to the invention can be designed e.g. as a boot lid for amotor vehicle. However, the exterior autobody part according to theinvention can be utilized in a number of other positions in the bodypanelling of a motor vehicle, such as a passenger car or a truck.

Accordingly, FIG. 3 shows an external perspective view of the driver'scab 28 of a truck, wherein one of the body panels 29 which are visiblein FIG. 3 is constituted of an exterior autobody part according to theinvention, designed as a so-called wind deflector 29. Even if invisiblein FIG. 3, a corresponding wind deflector is present on the oppositeside of the shown driver's cab. In FIG. 3, three other conceivable,advantageous positions 29′, 29″, 29′″ for exterior autobody partsaccording to the invention are also indicated.

What is claimed is:
 1. A material batch for vacuum forming an exteriorautobody part of reinforced plastic, intended to be mounted on a motorvehicle, said material batch comprising load-bearing layers and surfacelayers, wherein said load-bearing layers comprise fiber-reinforcedthermoplastic which creates internal cavities in the exterior autobodypart after the vacuum forming, and/or that said surface layers and saidload-bearing layers comprising fiber-reinforced thermoplastic provideone or several recesses in the exterior autobody part after the vacuumforming, so that said surface layers and load-bearing layers togetherwith said cavities and/or recesses provide a load-bearing materialstructure of the vacuum-formed exterior autobody part after the vacuumforming.
 2. A material batch according to claim 1, wherein said materialbatch provides at least one decorative layer between said surface layersand load-bearing layers, and that said surface layers and saiddecorative layers after vacuum forming together provide at least oneouter surface which provides the main portion of the visual effect andthe surface properties which the exterior autobody part should exhibitwhen mounted onto a motor vehicle, and that said surface layers,decorative layers and load-bearing layers all comprise a thermoplasticand are intended to be formed together under heating in order to providesaid exterior autobody part.
 3. A material batch according to claim 1,wherein a structural layer comprising thermoplastic material is providedbetween said decorative layer and load-bearing layer.
 4. A materialbatch according to claim 1, wherein said material batches, counted froma first external surface to a second, opposite external surface of theexterior autobody part, comprises a surface layer, a decorative layer, astructural layer, a load-bearing layer, a structural layer, a decorativelayer and a surface layer.
 5. A material batch according to claim 1,wherein the decorative layer and/or the structural layers comprise a dyeor a pigment.
 6. A material batch according to claim 1, wherein saidload-bearing layers comprise reinforcement fibers selected from thegroup consisting of glass-fibers, carbon fibers, kevlar fibers, nomexfibers, polyester fibers and aramide fibers.
 7. A material batchaccording to claim 1, wherein said material batches include at least onethermoplastic selected from the group consisting of ABS, PMMA and PP. 8.An exterior autobody part of reinforced plastic according to claim 1,which is intended to be mounted on a motor vehicle, wherein saidexterior autobody part has been vacuum-formed from one or severalmaterial batches.
 9. An exterior autobody part of reinforced plasticaccording to claim 8, wherein said exterior autobody part comprisesrecycled material originating from other exterior autobody parts.
 10. Anexterior autobody part of reinforced plastic according to claim 8,wherein said exterior autobody part is designed as a boot lid for amotor vehicle.
 11. An exterior autobody part of reinforced plasticaccording to claim 8, wherein said exterior autobody part is designed asa wind deflector for a motor vehicle.